Andrew Gardner, Amnesty International's researcher on Turkey, who is currently in Istanbul, said: "Following a night of shocking police violence, the authorities are now denying due process to those they have detained.

"The police must released them immediately or disclose their location and allow access to family members and lawyers.

"I did not see any violence being used by the protesters against the police while I was observing the protests in Taksim or in nearby Cihangir from 8.30pm until the early hours of the morning. During this time police continually attacked protesters with tear gas and water cannon."